Surface enhanced Raman scattering-based lateral flow immunosensor for sensitive detection of aflatoxin M₁ in urine

Aflatoxin M₁ (AFM₁) is generally used as a biomarker in urine for the assessment of aflatoxin exposure in humans and animals. However, there is no approach for the rapid and on-site monitoring of AFM₁ level in urine. Here, we report a surface enhanced Raman scattering (SERS)-based lateral flow immunosensor built for such a purpose. Raman molecule 5,5-dithiobis-2-nitrobenzoic acid and anti-AFM₁ monoclonal antibody were conjugated with Au (core)@Ag (shell) nanoparticle to serve as SERS nanoprobe. AFM₁-bovine serum albumin was conjugated with gold nanoparticle and then applied onto nitrocellulose membrane as a visible "GOLD" test line. Quantitation of AFM₁ was performed by the readout of Raman signal from the SERS nanoprobes captured on the test line. After optimizing experimental parameters, the detection limit of this immunosensor can achieve as low as 1.7 pg/mL of AFM₁ in urine, which is far below the recommended tolerable level (30 pg/mL) of AFM₁ in urine. The spiking experiment yielded 93.8%-111.3% recovery with coefficients of variation below 17% demonstrating high assay accuracy and precision. Moreover, this immunosensing assay is fast with an assay time below 20 min. Therefore, the developed immunosensor is a promising tool for the rapid assessment of aflatoxin exposure in the field.